Rabies virus (RV) based vaccine vectors induce potent cellular and humoral anti-HIV responses in mice and in rhesus macaques and can provide protection against an HIV-1 like disease in monkeys. However, there is also evidence that such vectors can be improved. Here we perform a detailed study of the activation pattern of RV-infected DCs, which will guide us to construct improved RV vectors. Moreover, we will analyze the impact of type I interferons on DC activation and on CCR7 expression for DC migration. We will analyze the immunogenicity and pathogenicity of such vectors in a mouse model, compare them with Newcastle Disease virus and vesicular stomatitis-based vaccine vectors, and prioritize their use for studies in rhesus macaques. Two specific Aims are proposed: Specific Aim 1. Determine the activation state of DCs after infection with RV-based HIV-1 vaccine vectors and analyze the impact of type I interferon expression by a recombinant RV. Test the hypothesis that interferon type I increases DCactivation. Determine the role of CCR7 expression on DC migration. Specific Aim 2 Immunizations of improved NSV HIV-1 vaccine vectors in mice and rhesus macaques Determine the impact of the innate immune response on the adaptive anti-HIV-1 immune response after infection with optimized RV vectors. Test the hypothesis that activation of innate immune responses reduces vector pathogenicity. Test the hypothesis that two viral vectors induce more potent responses against the expressed HIV-1 antigens than a single vector. Study the efficiency of optimized viral vectors in the rhesus macaque / SIV challenge model system. RELEVANCE (See instructions): A vaccine that prevents HIV infection or at least prevents AIDS would have a great impact on human health.